It is well recognized that wet processing in the textile industry is a major source of energy consumption. With the advent of high energy costs, and concern as to the availability of oil and natural gas, considerable effort has been expended in reducing energy usage for wet processing techniques such as bleaching, dyeing, printing and finishing.
A technology which has developed as a result of energy conservation research in the textile field is the use of foams for wet processing. By foaming techniques, the amount of liquid applied to the textiles is reduced substantially thereby greatly lowering the amount of energy required to dry the product. Not only is there a saving of energy, but foaming also permits increased productivity and a variety of other advantages.
Known foaming techniques generally utilize metering rolls and/or doctor blades for applying the correct amount of foam to the textile. When using these techniques for a product such as a pile carpet, wherein uniform penetration is important, either the carpet weight must be kept low, or vacuum slots and squeeze rolls are required to achieve acceptable penetration of liquid into the pile. Additionally, the foam must have a high air-to-liquid ratio (sometimes called a "blow ratio") so as to have sufficient viscosity to be uniformly applied by the roll and blade arrangements.
Various additional considerations of foaming techniques in the textile industry are discussed in the following articles:
"Application Techniques for Foam Dyeing and Finishing" by Dr. Werner Hartmann, appearing in the Canadian Textile Journal, April, 1980, p. 55; PA0 "New European Dye Technology", appearing in Textile Industries, May, 1980, p. 30; PA0 "Foam Processing Technology" by Richard J. Lyons, appearing in American Dyestuff Reports, April 1980, p. 22; and PA0 "Foam Finishing Technology: The Controlled Application of Chemicals to a Moving Substrate", appearing in Textile Chemists and Colorists, December, 1978, p. 269/37.
The latter generally discloses an arrangement for applying foam under pressure to a fabric. This, of course, requires control of the applicator whereby the pressure is maintained at level which will permit uniform application of the foam.